In general, a library apparatus includes a storage rack which stores, for example, hundreds of storage media such as magnetic tapes and optical discs and a drive which writes data to the storage media and reads data from the storage media.
The library apparatus is provided with a conveying robot which conveys a storage medium in a housing. The conveying robot extracts a storage medium from the storage rack so as to convey the storage medium to the drive or conveys a storage medium received from the drive to the storage rack so as to store the storage medium in the storage rack. As described above, since a storage medium is automatically conveyed between the storage rack and the drive by the conveying robot in the library apparatus, writing of data to the storage media stored in the storage rack and reading of data from the storage media are automatically performed.
Furthermore, some library apparatuses have two conveying robots which independently move in case of a failure of one of the conveying robots. Furthermore, in some of such library apparatuses, when one of the conveying robots fails, the other conveying robot moves the failed conveying robot to an escape area so that the failed conveying robot does not disturb conveying of storage media. Thereafter, the conveying robot which does not fail conveys the storage media until the failed robot has been repaired and recovered by a maintenance worker.
The related arts are disclosed in Japanese Laid-open Patent Publication Nos. 2005-251350, 2000-285566, and 2007-226873.